Question

In which of the following, the work done by the mentioned force is negative?

• A. The work done by the tension of the cable while the lift is ascending.
• B. The work done by the gravitational force when a body slides down an inclined place.
• C. The work done by the applied force in maintaining uniform motion of a block on a rough horizontal surface.
• D. The work done by the gravitational force when a body is thrown up.

Answer 1

The correct option is D The work done by the gravitational force when a body is thrown up.

When a body is thrown up the gravitational force acts opposite to the displacement of the body. The work done being a dot product of force and displacement vectors, becomes negative as cosine of 180 degrees is -1.